Hydrocarbon dehydrogenation using a platinum or palladium, rhodium, nickel, alkaline or alkaline earth metal catalyst

ABSTRACT

Dehydrogenatable hydrocarbons are dehydrogenated by contacting them, at dehydrogenation conditions, with a catalytic composite comprising a combination of catalytically effective amounts of a platinum or palladium component, a rhodium component, and a nickel component with a porous carrier material. A specific example of the nonacidic catalytic composite disclosed herein is a combination of a platinum or palladium component, a rhodium component, a nickel component, and an alkali or alkaline earth component with a porous carrier material in amounts sufficient to result in a composite containing about 0.01 to 2 wt. % platinum or palladium, about 0.01 to about 2 wt. % rhodium, about 0.01 to about 5 wt. % nickel and about 0.1 to about 5 wt. % alkali metal or alkaline earth metal. A preferred modifying component for the disclosed catalytic composites is a Group IVA metallic component.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of my prior, copending application Ser.No. 667,340 filed Mar. 16, 1976; which in turn is a continuation-in-partof my prior application Ser. No. 490,171 filed July 19, 1974 and issuedApr. 6, 1976 as U.S. Pat. No. 3,948,762. All of the teachings of theseprior applications are specifically incorporated herein by reference.

The subject of the present invention is, broadly, an improved method fordehydrogenating a dehydrogenatable hydrocarbon to produce a hydrocarbonproduct containing the same number of carbon atoms but fewer hydrogenatoms. In another aspect, the present invention involves a method ofdehydrogenating normal paraffin hydrocarbons containing 4 to 30 carbonatoms per molecule to the corresponding normal mono-olefin with minimumproduction of side products. In yet another aspect, the presentinvention relates to a novel nonacidic multimetallic catalytic compositecomprising a combination of catalytically effective amounts of aplatinum or palladium component, a rhodium component, a nickelcomponent, and an alkali or alkaline earth component with a porouscarrier material. This nonacidic composite has highly beneficialcharacteristics of activity, selectivity, and stability when it isemployed in the dehydrogenation of dehydrogenatable hydrocarbons such asaliphatic hydrocarbons, naphthene hydrocarbons, and alkylaromatichydrocarbons.

The conception of the present information followed from my search for anovel catalytic composite possessing a hydrogenation-dehydrogenationfunction, a controllable cracking function, and superior conversion,selectivity, and stability characteristics when employed in hydrocarbonconversion processes that have traditionally utilized dual-functioncatalytic composites. In my prior application, I disclosed a significantfinding with respect to a multimetallic catalytic composite meetingthese requirements. More specifically, I determined that a combinationof rhodium and nickel can be utilized, under certain conditions, tobeneficially interact with the platinum or palladium component of adual-function catalyst with a resulting marked improvement in theperformance of such a catalyst. Now I have ascertained that a catalyticcomposite, comprising a combination of catalytically effective amountsof a platinum or palladium component, a rhodium component, and a nickelcomponent with a porous carrier material can have superior activity,selectivity, and stability characteristics when it is employed in adehydrogenation process if these components are uniformly dispersed inthe porous carrier material in the amounts specified hereinafter and ifthe oxidation state of the metallic ingredients are carefully controlledso that substantially all of the platinum or palladium, rhodium andnickel components are present in the elemental metallic state. Asindicated in my prior application, I have also found that a preferredmodifying component for this catalytic composite is a Group IVA metalliccomponent. I have discerned, moreover, that a particularly preferredmultimetallic catalytic composite of this type contains not only aplatinum or palladium component, a rhodium component, and a nickelcomponent, but also an alkali or alkaline earth component in an amountsufficient to ensure that the resulting catalyst is nonacidic.

The dehydrogenation of dehydrogenatable hydrocarbons is an importantcommercial process because of the great and expanding demand fordehydrogenated hydrocarbons for use in the manufacture of variouschemical products such as detergents, plastics, synthetic rubbers,pharmaceutical products, high octane gasolines, perfumes, drying oils,ion-exchange resins, and various other products well known to thoseskilled in the art. One example of this demand is in the manufacture ofhigh octane gasoline by using C₃ and C₄ mono-olefins to alkylateisobutane. Another example of this demand is in the area ofdehydrogenation of normal paraffin hydrocarbons to produce normalmono-olefins having 4 to 30 carbon atoms per molecule. These normalmono-olefins can, in turn, be utilized in the synthesis of a vast numberof other chemical products. For example, derivatives of normalmono-olefins have become of substantial importance to the detergentindustry where they are utilized to alkylate an aromatic, such asbenzene, with subsequent transformation of the product arylalkane into awide variety of biodegradable detergents such as the alkylaryl sulfonatetypes of detergents which are most widely used today for household,industrial, and commercial purposes. Still another large class ofdetergents produced from these normal mono-olefins are the oxyalkylatedphenol derivatives in which the alkylphenol base is prepared by thealkylation of phenol with these normal mono-olefins. Still another typeof detergents produced from these normal mono-olefins are thebiodegradable alkylsulfonates formed by the direct sulfation of thenormal mono-olefins. Likewise, the olefin can be subjected to directsulfonation with sodium bisulfite to make biodegradable alkylsulfonates.As a further example, these mono-olefins can be hydrated to producealcohols which then, in turn, can be used to produce plasticizers and/orsynthetic lube oils.

Regarding the use of products made by the dehydrogenation ofalkylaromatic hydrocarbons, they find wide application in the petroleum,petrochemical, pharmaceutical, detergent, plastic, and the likeindustries. For example, ethylbenzene is dehydrogenated to producestyrene which is utilized in the manufacture of polystyrene plastics,styrene-butadiene rubber, and the like products. Isopropylbenzene isdehydrogenated to form alpha-methylstyrene which, in turn, isextensively used in polymer formation and in the manufacture of dryingoils, ion-exchange resins, and the like materials.

Responsive to this demand for these dehydrogenation products, the arthas developed a number of alternative methods to produce them incommercial quantities. One method that is widely utilized involves theselective dehydrogenation of a dehydrogenatable hydrocarbon bycontacting the hydrocarbon with a suitable catalyst at dehydrogenationconditions. As is the case with most catalytic procedures, the principalmeasure of effectiveness for this dehydrogenation method involves theability to perform its intended function with minimum interference ofside reactions for extended periods of time. The analytical terms usedin the art to broadly measure how well a particular catalyst performsits intended functions in a particular hydrocarbon conversion reactionare activity, selectivity, and stability, and for purposes of discussionhere, these terms are generally defined for a given reactant as follows:(1) activity is a measure of the catalyst's ability to convert thehydrocarbon reactant into products at a specified severity level whereseverity level means the specific reaction conditions used -- that is,the temperature, pressure, contact time, and presence of diluents suchas H₂ ; (2) selectivity usually refers to the amount of desired productor products obtained relative to the amount of the reactant charged orconverted; (3) stability refers to the rate of change with time of theactivity and selectivity parameters -- obviously the smaller rateimplying the more stable catalyst. More specifically, in adehydrogenation process, activity commonly refers to the amount ofconversion that takes place for a given dehydrogenatable hydrocarbon ata specified severity level and is typically measured on the basis ofdisappearance of the dehydrogenatable hydrocarbon; selectivity istypically measured by the amount, calculated on a mole percent ofconverted dehydrogenatable hydrocarbon basis, of the desireddehydrogenated hydrocarbon obtained at the particular activity orseverity level; and stability is typically equated to the rate of changewith time of activity as measured by disappearance of thedehydrogenatable hydrocarbon and of selectivity as measured by theamount of desired dehydrogenated hydrocarbon produced. Accordingly, themajor problem facing workers in the hydrocarbon dehydrogenation art isthe development of a more active and selective catalytic composite thathas good stability characteristics.

I have now found a multimetallic catalytic composite which possessesimproved activity, selectivity, and stability when it is employed in aprocess for the dehydrogenation of dehydrogenatable hydrocarbons. Inparticular, I have determined that the use of a multimetallic catalyst,comprising a combination of catalytically effective amounts of aplatinum or palladium component, a rhodium component, a nickel componentand, in the preferred case, a Group IVA metallic component with a porousrefractory carrier material, can enable the performance of adehydrogenation process to be substantially improved if the metalliccomponents are uniformly dispersed throughout the carrier material inthe amounts specified hereinafter and if their oxidation states arecarefully controlled to be in the states hereinafter specified.Moreover, particularly good results are obtained when this composite iscombined with an amount of an alkali or alkaline earth componentsufficient to ensure that the resulting catalyst is nonacidic andutilized to produce dehydrogenated hydrocarbons containing the samecarbon structure as the reactant hydrocarbon but fewer hydrogen atoms.This nonacidic composite is particularly useful in the dehydrogenationof long chain normal paraffins to produce the corresponding normalmono-olefin with minimization of side reactions such as skeletalisomerization, aromatization, cracking and polyolefin formation. In sumthe present invention involves the significant finding that acombination of a rhodium component and a nickel component can beutilized under the circumstances specified herein to beneficiallyinteract with and promote a dehydrogenation catalyst containing aplatinum or palladium component and, in an especially preferred case, aGroup IVA metallic component.

It is, accordingly, one object of the present invention to provide anovel method for the dehydrogenation of dehydrogenatable hydrocarbonsutilizing a multimetallic catalytic composite comprising catalyticallyeffective amounts of a platinum or palladium component, a rhodiumcomponent, and a nickel component combined with a porous carriermaterial. A second object is to provide a novel nonacidic catalyticcomposite having superior performance characteristics when utilized in adehydrogenation process. Another object is to provide an improved methodfor the dehydrogenation of normal paraffin hydrocarbons to producenormal mono-olefins which method minimizes undesirable side reactionssuch as cracking, skeletal isomerization, polyolefin formation,disproportionation and aromatization.

In brief summary, one embodiment of the present invention involves amethod for dehydrogenating a dehydrogenatable hydrocarbon whichcomprises contacting the hydrocarbon at dehydrogenation conditions witha multimetallic catalytic composite comprising a porous carrier materialcontaining a uniform dispersion of catalytically effective amounts of aplatinum or palladium component, a rhodium component and a nickelcomponent. Moreover, substantially all of the platinum or palladium,rhodium and nickel components are present in the composite in theelemental metallic state and in amounts, calculated on an elementalbasis, sufficient to result in the composite containing about 0.01 toabout 2 wt. % platinum or palladium, about 0.01 to about 2 wt. %rhodium, and about 0.01 to about 5 wt. % nickel.

A second embodiment relates to the dehydrogenation method described inthe first embodiment wherein the dehydrogenatable hydrocarbon is analiphatic compound containing 2 to 30 carbon atoms per molecule.

A third embodiment involves the dehydrogenation method described in thefirst or second embodiment wherein the catalytic composite used thereinalso contains about 0.01 to about 5 wt % of a Group IVA metal andwherein substantially all of the Group IVA is present in an oxidationstate above that of the corresponding elemental metal.

A fourth embodiment comprehends a nonacidic catalytic compositecomprising a porous carrier material having uniformly dispersed thereincatalytically effective amounts of a platinum or palladium component, arhodium component, a nickel component, and an alkali or alkaline earthcomponent. These components are preferably present in amounts sufficientto result in the catalytic composite containing, on an elemental basis,about 0.01 to about 2 wt. % platinum or palladium, about 0.1 to about 5wt. % of the alkali metal or alkaline earth metal, about 0.01 to about 2wt. % rhodium, and about 0.01 to about 5 wt. % nickel. In addition,substantially all of the platinum or palladium, rhodium and nickelcomponents are present in the elemental metallic state and substantiallyall of the alkali or alkaline earth component is present in an oxidationstate above that of the elemental metal.

Another embodiment comprises the nonacidic catalytic composite definedin the fourth embodiment combined with a Group IVA metallic component inan amount sufficient to incorporate, on an elemental basis, about 0.01to about 5 wt. % Group IVA metal and in a manner such that substantiallyall of the Group IVA metal is present in an oxidation state above thatof the corresponding metal.

Yet another embodiment pertains to a method for dehydrogenating adehydrogenatable hydrocarbon which comprises contacting the hydrocarbonwith the nonacidic catalytic composite described in the fourth or fifthembodiment at dehydrogenation conditions.

Other objects and embodiments of the present invention involve specificdetails regarding essential and preferred catalytic ingredients,preferred amounts of ingredients, effective methods of multimetalliccomposite preparation, suitable dehydrogenatable hydrocarbons, operatingconditions for use in the dehydrogenation process, and the likeparticulars. These are hereinafter given in the following detaileddiscussion of each of these facets of the present invention. It is to benoted that (1) the term "nonacidic" means that the catalyst producesless than 10% conversion of 1-butene to isobutylene when tested atdehydrogenation conditions and, preferably, less than 1% and (2) theexpression "uniformly dispersed throughout a carrier material" isintended to mean that the amount of the subject component, expressed ona weight percent basis, is approximately the same in any reasonablydivisible portion of the carrier material as it is in gross.

Regarding the dehydrogenatable hydrocarbon that is subjected to themethod of the present invention, it can, in general, be an organiccompound having 2 to 30 carbon atoms per molecule and containing atleast one pair of adjacent carbon atoms having hydrogen attachedthereto. That is, it is intended to include within the scope of thepresent invention, the dehydrogenation of any organic compound capableof being dehydrogenated to produce products containing the same numberof carbon atoms but fewer hydrogen atoms, and capable of being vaporizedat the dehydrogenation temperatures used herein. More particularly,suitable dehydrogenatable hydrocarbons are: aliphatic compoundscontaining 2 to 30 carbon atoms per molecule, alkylaromatic hydrocarbonswhere the alkyl group contains 2 to 6 carbon atoms, and naphthenes oralkyl-substituted naphthenes. Specific examples of suitabledehydrogenatable hydrocarbons are: (1) alkanes such as ethanes, propane,n-butane, isobutane, n-pentane, isopentane, n-hexane, 2-methylpentane,3-methylpentane, 2,2-dimethylbutane, n-heptane, 2-methylhexane,2,2,3-trimethylbutane, and the like compounds; (2) naphthenes such ascyclopentane, cyclohexane, methylcyclopentane, ethylcyclopentane,n-propylcyclopentane, 1,3-dimethylcyclohexane, and the like compounds;and (3) alkylaromatics such as ethylbenzene, n-butylbenzene,1,3,5-triethylbenzene, isopropylbenzene, isobutylbenzene,ethylnaphthalene, and the like compounds.

In a preferred embodiment, the dehydrogenatable hydrocarbon is a normalparaffin hydrocarbon having about 4 to 30 carbon atoms per molecule. Forexample, normal paraffin hydrocarbons containing about 10 to 18 carbonatoms per molecule are dehydrogenated by the subject method to producethe corresponding normal mono-olefin which can, in turn, be alkylatedwith benzene and sulfonated to make alkylbenzene sulfonate detergentshaving superior biodegradability. Likewise, n-alkanes having 10 to 18carbon atoms per molecule can be dehydrogenated to the correspondingnormal mono-olefin which, in turn, can be sulfonated or sulfated to makeexcellent detergents. Similarly, n-alkanes having 6 to 10 carbon atomscan be dehydrogenated to form the corresponding mono-olefin which can,in turn, by hydrated to produce valuable alcohols. Preferred feedstreams for the manufacture of detergent intermediates contain a mixtureof 4 or 5 adjacent normal paraffin homologues such as C₁₀ to C₁₃, C₁₁ toC₁₄, C₁₁ to C₁₅ and the like mixtures.

The multimetallic catalyst used in the present invention comprises aporous carrier material or support having combined therewith a uniformdispersion of catalytically effective amounts of a platinum or palladiumcomponent, a rhodium component, a nickel component, and, in preferredcases, an alkali or alkaline earth component and/or a Group IVA metalliccomponent.

Considering first the porous carrier material utilized in the presentinvention, it is preferred that the material be a porous, adsorptive,high-surface area support having a surface area of about 25 to about 500m² /g. The porous carrier material should be relatively refractory tothe conditions utilized in the dehydrogenation process, and it isintended to include within the scope of the present invention carriermaterials which have traditionally been utilized in dual-functionhydrocarbon conversion catalysts, such as: (1) activated carbon, coke,charcoal; (2) silica or silica gel, silicon carbide, clays, andsilicates including those synthetically prepared and naturallyoccurring, which may or may not be acid treated, for example, attapulgusclay, china clay, diatomaceous earth, fuller's earth, kaolin,kieselguhr, etc.; (3) ceramics, porcelain, crushed firebrick, bauxite;(4) refractory inorganic oxides such as alumina, titanium dioxide,zirconium dioxide, chromium oxide, zinc oxide, magnesia, thoria, boria,silica-alumina, silica-magnesia, chromia-alumina, alumina-boria,silica-zirconia, etc.; (5) crystalline zeolitic aluminosilicates such asnaturally occurring or synthetically prepared mordenite and/orfaujasite, either in the hydrogen form or in a form which has beentreated with multivalent cations; (6) spinels such as MgAl₂ O₄, FeAl₂O₄, ZnAl₂ O₄, MnAl₂ O₄, CaAl₂ O₄ and other like compounds having theformula MO.Al₂ O₃ where M is a metal having a valence of 2; and (7)combinations of elements from one or more of these groups. The preferredporous carrier material for use in the present invention are refractoryinorganic oxides, with best results obtained with an alumina carriermaterial. Suitable alumina materials are the crystalline aluminas knownas the gamma-, eta-, and theta-alumina, with gamma- or eta-aluminagiving best results. In addition, in some embodiments the aluminacarrier material may contain minor proportions of other well-knownrefractory inorganic oxides such as silica, zirconia, magnesia, etc.;however, the preferred support is substantially pure gamma- oreta-alumina. Preferred carrier materials have an apparent bulk densityof about 0.2 to about 0.7 g/cc and surface area characteristics suchthat the average pore diameter is about 20 to about 30 Angstroms, thepore volume is about 0.1 to about 1 cc/g and the surface area is about100 to about 500 m² /g. In general, best results are typically obtainedwith a gamma-alumina carrier material which is used in the form ofspherical particles having: a relatively small diameter (i.e. typicallyabout 1/16 inch), an apparent bulk density of about 0.2 to about 0.6(most preferably about 0.3) g/cc, a pore volume of about 0.4 cc/g, and asurface area of about 150 to about 200 m² /g.

The preferred alumina carrier material may be prepared in any suitablemanner and may be synthetically prepared or natural occurring. Whatevertype of alumina is employed, it may be activated prior to use by one ormore treatments including drying, calcination, steaming, etc., and itmay be in a form known as activated alumina, activated alumina ofcommerce, porous alumina, alumina gel, etc. For example, the aluminacarrier may be prepared by adding a suitable alkaline reagent, such asammonium hydroxide to a salt of aluminum such as aluminum chloride,aluminum nitrate, etc., in an amount to form an aluminum hydroxide gelwhich upon drying and calcining is converted to alumina. The aluminacarrier may be formed in any desired shape such as spheres, pills,cakes, extrudates, powders, granules, etc., and utilized in any desiredsize. For the purpose of the present invention, a particularly preferredform of alumina is the sphere; and alumina spheres may be continuouslymanufactured by the well-known oil drop method which comprises: formingan alumina hydrosol by any of the techniques taught in the art andpreferably by reacting aluminum metal with hydrochloric acid, combiningthe resulting hydrosol with a suitable gelling agent and dropping theresultant mixture into an oil bath maintained at elevated temperatures.The droplets of the mixture remain in the oil bath until they set andform hydrogel spheres. The spheres are then continuously withdrawn fromthe oil bath and typically subjected to specific aging treatments in oiland an ammoniacal solution to further improve their physicalcharacteristics. The resulting aged and gelled particles are then washedand dried at a relatively low temperature of about 300° F. to about 400°F. and subjected to a calcination procedure at a temperature of about850° F. to about 1300° F. for a period of about 1 to about 20 hours. Itis a good practice to subject the calcined particles to a hightemperature treatment with steam in order to remove undesired acidiccomponents such as residual chloride. This procedure effects conversionof the alumina hydrogel to the corresponding crystalline gamma-alumina.See the teachings of U.S. Pat. No. 2,620,314 for additional details.

One essential ingredient of the present catalytic composite is a nickelcomponent. This component may be present in the composite as anelemental metal, or in chemical combinations with one or more of theother ingredients of the composite, or as a chemical compound of nickelsuch as nickel oxide, sulfide, halide, oxychloride, aluminate and thelike. Best results are obtained when the composite containssubstantially all of this component in the elemental state, and thepreferred preparation procedure which is given in Example 1 is believedto result in this condition. The nickel component may be utilized in thecomposite in any amount which is catalytically effective, with thepreferred amount being about 0.01 to about 5 wt. % thereof, calculatedon an elemental nickel basis. Typically, best results are obtained withabout 0.05 to about 2 wt. % nickel. It is, additionally, preferred toselect the specific amount of nickel from within this broad weight rangeas a function of the amount of the platinum or palladium component, onan atomic basis, as is explained hereinafter.

The nickel component may be incorporated into the catalytic composite inany suitable manner known to those skilled in the catalyst formulationart. In addition, it may be added at any stage of the preparation of thecomposite -- either during preparation of the carrier material orthereafter -- since the precise method of incorporation used is notdeemed to be critical. However, best results are thought to be obtainedwhen the nickel component is relatively uniformly distributed throughoutthe carrier material, and the preferred procedures are the ones that areknown to result in a composite having a relatively uniform distribution.One acceptable procedure for incorporating this component into thecomposite involves cogelling the nickel component during the preparationof the preferred carrier material, alumina. This procedure usuallycomprehends the addition of a soluble, decomposable compound of nickelsuch as nickel nitrate to the alumina hydrosol before it is gelled. Theresulting mixture is then finished by conventional gelling, aging,drying, and calcination steps as explained hereinbefore. One preferredway of incorporating this component is an impregnation step wherein theporous carrier material is impregnated with a suitable nickel-containingsolution either before, during, or after the carrier material iscalcined. Preferred impregnation solutions are aqueous solutions ofwater-soluble, decomposable nickel compounds such as nickel bromate,nickel bromide, nickel perchlorate, nickel chloride, nickel fluoride,nickel iodide, nickel nitrate, nickel sulfate, and the like compounds.Best results are ordinarily obtained when the impregnation solution isan aqueous solution of nickel chloride or nickel nitrate. This nickelcomponent can be added to the carrier material, either prior to,simultaneously with, or after the other metallic components are combinedtherewith. Best results are usually achieved when this component isadded simultaneously with the platinum or palladium and rhodiumcomponents. In fact, excellent results are obtained, as reported in theexamples, with a one step impregnation procedure using an aqueoussolution comprising chloroplatinic acid, nickel nitrate, nitric acid andrhodium nitrate.

A second essential ingredient of the subject catalyst is the platinum orpalladium component. That is, it is intended to cover the use ofplatinum or palladium or mixtures thereof as a second component of thepresent composite. It is an essential feature of the present inventionthat substantially all of this platinum or palladium component existswithin the final catalytic composite in the elemental metallic state.Generally, the amount of this component present in the final catalystcomposite is small compared to the quantities of the other componentscombined therewith. In fact, the platinum or palladium componentgenerally will comprise about 0.01 to about 2 wt. % of the finalcatalytic composite, calculated on an elemental basis. Excellent resultsare obtained when the catalyst contains about 0.05 to about 1 wt. % ofplatinum or palladium metal.

This platinum or palladium component may be incorporated in thecatalytic composite in any suitable manner known to result in arelatively uniform distribution of this component in the carriermaterial such as coprecipitation or cogelation, ion exchange orimpregnation. The preferred method of preparing the catalyst involvesthe utilization of a soluble, decomposable compound of platinum orpalladium to impregnate the carrier material in a relatively uniformmanner. For example, this component may be added to the support bycommingling the latter with an aqueous solution of chloroplatinic orchloropalladic acid. Other water-soluble compounds of platinum orpalladium may be employed in impregnation solutions and include ammoniumchloroplatinate, bromoplatinic acid, platinum trichloride, platinumtetrachloride hydrate, platinum dichlorocarbonyl dichloride,dinitrodiaminoplatinum, sodium tetranitroplatinate (II), palladiumchloride, palladium nitrate, palladium sulfate, diamminepalladium (II)hydroxide, tetramminepalladium (II) chloride, etc. The utilization of aplatinum or palladium chloride compound, such as chloroplatinic orchloropalladic acid, is ordinarily preferred. Hydrogen chloride, nitricacid or the like acid is also generally added to the impregnationsolution in order to further facilitate the uniform distribution of themetallic components throughout the carrier material. In addition, it isgenerally preferred to impregnate the carrier material after it has beencalcined in order to minimize the risk of washing away the valuableplatinum or palladium compounds; however, in some cases it may beadvantageous to impregnate the carrier material when it is in a gelledstate.

Yet another essential ingredient of the present catalytic composite is arhodium component. It is of fundamental importance that substantiallyall of the rhodium component exists within the catalytic composite ofthe present invention in the elemental metallic state and thesubsequently described reduction procedure is designed to accomplishthis objective. The rhodium component may be utilized in the compositein any amount which is catalytically effective, with the preferredamount being about 0.01 to about 2 wt. % thereof, calculated on anelemental basis. Typically, best results are obtained with about 0.05 toabout 1 wt. % rhodium. It is additionally preferred to select thespecific amount of rhodium from within this broad weight range as afunction of the amount of the platinum or palladium component, on anatomic basis, as is explained hereinafter.

This rhodium component may be incorporated into the catalytic compositein any suitable manner known to those skilled in the catalystformulation art which results in a relatively uniform dispersion ofrhodium in the carrier material. In addition, it may be added at anystage of the preparation of the composite -- either during preparationof the carrier material or thereafter -- and the precise method ofincorporation used is not deemed to be critical. However, best resultsare obtained when the rhodium component is relatively uniformlydistributed throughout the carrier material, and the preferredprocedures are the ones known to result in a composite having thisrelatively uniform distribution. One acceptable procedure forincorporating this component into the composite involves cogelling orcoprecipitating the rhodium component during the preparation of thepreferred carrier material, alumina. This procedure usually comprehendsthe addition of a soluble, decomposable compound of rhodium such asrhodium nitrate or rhodium trichloride hydrate to the alumina hydrosolbefore it is gelled. The resulting mixture is then finished byconventional gelling, aging, drying, and calcination steps as explainedhereinbefore. A preferred way of incorporating this component is animpregnation step wherein the porous carrier material is impregnatedwith a suitable rhodium-containing solution either before, during, orafter the carrier material is calcined. Preferred impregnation solutionsare aqueous solutions of water soluble, decomposable rhodium compoundssuch as hexamminerhodium chloride, rhodium carbonylchloride, rhodiumtrichloride hydrate, rhodium nitrate, sodium hexachlororhodate (III),sodium hexanitrorhodate (III), rhodium sulfate, and the like compounds.Best results are ordinarily obtained when the impregnation solution isan aqueous solution of rhodium trichloride hydrate or rhodium nitrate.This component can be added to the carrier material, either prior to,simultaneously with, or after the other metallic components are combinedtherewith. Best results are usually achieved when this component isadded simultaneously with the platinum or palladium and rhodiumcomponents. In fact, excellent results are obtained, as reported in theexamples, with a one step impregnation procedure using an aqueoussolution comprising chloroplatinic or chloropalladic acid, rhodiumnitrate, nickel nitrate and nitric acid.

One especially preferred constituent of the instant multimetalliccatalytic composite is a Group IVA metallic component. By the use of thegeneric term "Group IVA metallic component" it is intended to cover themetals of Group IVA of the Periodic Table. More specifically, it isintended to cover; germanium, tin, lead, and mixtures of these metals.It is essential that substantially all of the Group IVA metalliccomponent is present in the final catalyst in an oxidation state abovethat of the elemental metal. In other words, this component may bepresent in chemical combination with one or more of the otheringredients of the composite, or as a chemical compound of the Group IVAmetal such as the oxide, sulfide, halide, oxyhalide, oxychloride,aluminate, and the like compounds. Based on the evidence currentlyavailable, it is believed that best results are obtained whensubstantially all of the Group IVA metallic component exists in thefinal composite in the form of the corresponding oxide such as the tinoxide, germanium oxide, and lead oxide, and the subsequently describedoxidation and reduction steps, that are preferably used in thepreparation of the instant composite, are believed to result in acatalytic composite which contains an oxide of the Group IVA metalliccomponent. Regardless of the state in which this component exists in thecomposite, it can be utilized therein in any amount which iscatalytically effective, with the preferred amount being about 0.01 toabout 5 wt. % thereof, calculated on an elemental basis and the mostpreferred amount being about 0.05 to about 2 wt. %. The exact amountselected within this broad range is preferably determined as a functionof the particular Group IVA metal that is utilized. For instance, in thecase where this component is lead, it is preferred to select the amountof this component from the low end of this range -- namely, about 0.01to about 1 wt. %. Additionally, it is preferred to select the amount oflead as a function of the amount of the platinum group component asexplained hereinafter. In the case where this component is tin, it ispreferred to select from a relatively broader range of about 0.05 toabout 2 wt. % thereof. And, in the preferred case, where this componentis germanium the selection can be made from the full breadth of thestated range -- specifically, about 0.01 to about 5 wt. %, with bestresults at about 0.05 to about 2 wt. %.

This Group IVA component may be incorporated in the composite in anysuitable manner known to the art to result in a uniform dispersion ofthe Group IVA moiety throughout the carrier material such as,coprecipitation or cogelation with the porous carrier material, ionexchange with the carrier material, or impregnation of the carriermaterial at any stage in its preparation. It is to be noted that it isintended to include within the scope of the present invention allconventional procedures for incorporating a metallic component in acatalytic composite, and the particular method of incorporation used isnot deemed to be an essential feature of the present invention so longas the Group IVA component is uniformly distributed throughout theporous carrier material. One acceptable method of incorporating theGroup IVA component into the catalytic composite involves cogelling theGroup IVA component during the preparation of the preferred carriermaterial, alumina. This method typically involves the addition of asuitable soluble compound of the Group IVA metal of interest to thealumina hydrosol. The resulting mixture is then commingled with asuitable gelling agent, such as a relatively weak alkaline reagent, andthe resulting mixture is thereafter preferably gelled by dropping into ahot oil bath as explained hereinbefore. After aging, drying, andcalcining the resulting particles, there is obtained an intimatecombination of the oxide of the Group IVA metal and alumina. Onepreferred method of incorporating this component into the compositeinvolves utilization of a soluble decomposable compound of theparticular Group IVA metal of interest to impregnate the porous carriermaterial either before, during, or after the carrier material iscalcined. In general, the solvent used during this impregnation step isselected on the basis of its capability to dissolve the desired GroupIVA compound without affecting the porous carrier material which is tobe impregnated; ordinarily, good results are obtained when water is thesolvent; thus the preferred Group IVA compounds for use in thisimpregnation step are typically water-soluble and decomposable. Examplesof suitable Group IVA compounds are: germanium difluoride, germaniumtetra-alkoxide, germanium dioxide, germanium tetrafluoride, germaniummonosulfide, tin chloride, tin bromide, tin dibromide di-iodide, tindichloride di-iodide, tin chromate, tin difluoride, tin tetraiodide, tinsulfate, tin tartrate, lead acetate, lead bromate, lead bromide, leadchlorate, lead chloride, lead citrate, lead formate, lead lactate, leadmalate, lead nitrate, lead nitrite, lead dithionate, and the likecompounds. In the case where the Group IVA component is germanium, apreferred impregnation solution is germanium tetrachloride dissolved inanhydrous alcohol. In the case of tin, tin chloride dissolved in wateris preferred. In the case of lead, lead nitrate dissolved in water ispreferred. Regardless of which impregnation solution is utilized, theGroup IVA component can be impregnated either prior to, simultaneouslywith, or after the other metallic components are added to the carriermaterial. Ordinarily, best results are obtained when this component isimpregnated simultaneously with the platinum or palladium, rhodium andnickel components of the composite. Likewise, best results areordinarily obtained when the Group IVA component is germanium oxide ortin oxide.

A highly preferred ingredient of the catalyst used in the presentinvention is the alkali or alkaline earth component. More specifically,this component is selected from the group consisting of the compounds ofthe alkali metals -- cesium, rubidium, potassium, sodium, and lithium --and of the alkaline earth metals -- calcium, strontium, barium, andmagnesium. This component exists within the catalytic composite in anoxidation state above that of the elemental metal such as a relativelystable compound such as the oxide or hydroxide, or in combination withone or more of the other components of the composite, or in combinationwith the carrier material such as, for example, in the form of an alkalior alkaline earth metal aluminate. Since as is explained hereinafter,the composite containing the alkali or alkaline earth component isalways calcined or oxidized in an air atmosphere before use in thedehydrogenation of hydrocarbons, the most likely state this componentexists in during use in the dehydrogenation reaction is thecorresponding metallic oxide such as lithium oxide, potassium oxide,sodium oxide, and the like. Regardless of what precise form in which itexists in the composite, the amount of this component utilized ispreferably selected to provide a nonacidic composite containing about0.1 to about 5 wt. % of the alkali metal or alkaline earth metal, and,more preferably, about 0.25 to about 3.5 wt. %. Best results areobtained when this component is a compound of lithium or potassium. Thefunction of this component is to neutralize any of the acidic materialsuch as halogen which may have been used in the preparation of thepresent catalyst so that the final catalyst is nonacidic.

This alkali or alkaline earth component may be combined with the porouscarrier material in any manner known to those skilled in the art toresult in a relatively uniform dispersion of this component throughoutthe carrier material with consequential neutralization of any acidicsites which may be present therein. Typically good results are obtainedwhen it is combined by impregnation, coprecipitation, ion-exchange, andthe like procedures. The preferred procedure, however, involvesimpregnation of the carrier material either before, during, or after itis calcined, or before, during, or after the other metallic ingredientsare added to the carrier material. Best results are ordinarily obtainedwhen this component is added to the carrier material after the platinumor palladium, rhodium, nickel and Group IVA components because thealkali metal or alkaline earth metal component acts to neutralize theacidic materials used in the preferred impregnation procedure for thesemetallic components. In fact, it is preferred to add the other metalliccomponents to the carrier material, oxidize the resulting composite in awet air stream at a high temperature (i.e. typically about 600° to 1000°F.), then treat the resulting oxidized composite with steam or a mixtureof air and steam at a relatively high temperature of about 800° to about1050° F. in order to remove at least a portion of any residual acidityand thereafter add the alkali metal or alkaline earth component.Typically, the impregnation of the carrier material with this componentis performed by contacting the carrier material with a solution of asuitable decomposable compound or salt of the desired alkali or alkalineearth metal. Hence, suitable compounds include the alkali metal oralkaline earth metal halides, sulfates, nitrates, acetates, carbonates,phosphates, and the like compounds. For example, excellent results areobtained by impregnating the carrier material after the other metalliccomponents have been combined therewith, with an aqueous solution oflithium nitrate or potassium nitrate.

Regarding the preferred amounts of the metallic components of thesubject catalyst, I have found it to be a beneficial practice to specifythe amounts of these metallic components not only on an absolute basisbut also as a function of the amount of the platinum or palladiumcomponent, expressed on an atomic basis. Quantitatively, the amount ofthe rhodium component is preferably sufficient to provide an atomicratio of rhodium to platinum or palladium metal of about 0.1:1 to about2:1, with best results obtained at an atomic ratio of about 0.25:1 toabout 1.5:1. Similarly, it is a good practice to specify the amount ofthe nickel component so that the atomic ratio of nickel to platinum orpalladium metal contained in the composite is about 0.2:1 to about 40:1,with the preferred range being about 1:1 to about 20:1. In the samemanner, the amount of the alkali or alkaline earth component isordinarily selected to produce a composite having an atomic ratio ofalkali metal or alkaline earth metal to platinum or palladium metal ofabout 5:1 to about 100:1 or more, with the preferred range being about10:1 to about 75:1. The amount of preferred Group IVA metallic componentis likewise selected so that the atomic ratio of Group IVA metal toplatinum or palladium metal is 0.05:1 to about 10:1, with best resultsobtained when this ratio is fixed on the basis of the individual GroupIVA species as follows: (1) for germanium, it is about 0.3:1 to 10:1 andmost preferably about 0.6:1 to 6:1; (2) for tin, it is about 0.1:1 to3:1 and most preferably about 0.5:1 to 1.5:1; and (3) for lead, it isabout 0.05:1 to 0.9:1 and most preferably about 0.1:1 to 0.75:1.

Another significant parameter for the instant nonacidic catalytst is the"total metals content" which is defined to be the sum of the platinum orpalladium component, the rhodium component, the nickel component, theGroup IVA metallic component (when it is used) and the alkali oralkaline earth component, calculated on an elemental metal basis. Goodresults are ordinarily obtained with the subject catalyst when thisparameter is fixed at a value of about 0.15 to about 5 wt. %, with bestresults ordinarily achieved at a metals loading of about 0.3 to about 4wt. %.

Integrating the above discussion of each of the essential and preferredcomponents of the catalytic composite used in the present invention, itis evident that an especially preferred nonacidic catalytic compositecomprises a combination of a platinum or palladium component, a rhodiumcomponent, a nickel component, and an alkali or alkaline earth componentwith an alumina carrier material in amounts sufficient to result in thecomposite containing from about 0.05 to about 1 wt. % platinum orpalladium, about 0.05 to about 1 wt. % rhodium, about 0.25 to about 3.5wt. % of the alkali metal or alkaline earth metal, and about 0.05 toabout 2 wt. % nickel.

Regardless of the details of how the components of the catalyst arecombined with the porous carrier material, the resulting multimetalliccomposite generally will be dried at a temperature of about 200° F. toabout 600° F. for a period of from about 2 to about 24 hours or more,and finally calcined or oxidized at a temperature of about 600° F. toabout 1100° F. in an air atmosphere for a period of about 0.5 to 10hours, preferably about 1 to about 5 hours, in order to convertsubstantially all the metallic components to the corresponding oxideform. When acidic components are present in any of the reagents used toeffect incorporation of any one of the components of the subjectcomposite, it is a good practice to subject the resulting composite to ahigh temperature treatment with steam or with a mixture of steam andair, either before, during or after this oxidation step in order toremove as much as possible of the undesired acidic components. Forexample, when the platinum or palladium component is incorporated byimpregnating the carrier material with chloroplatinic acid, it ispreferred to subject the resulting composite to a high temperaturetreatment with steam or a mixture of steam and air at a temperature ofabout 600° to 1100° F. in order to remove as much as possible of theundesired chloride.

The resultant oxidized catalytic composite is subjected to asubstantially water-free reduction step prior to its use in thedehydrogenation of hydrocarbons. This step is designed to selectivelyreduce the platinum or palladium, rhodium and nickel components to thecorresponding metals and to insure a uniform and finely divideddispersion of the metallic components throughout the carrier materialwhile maintaining the preferred Group IVA metallic and alkali oralkaline earth components in a positive oxidation state. It is a goodpractice to dry the oxidized catalyst prior to this reduction step bypassing a stream of dry air or nitrogen through same at a temperature ofabout 500° to 1100° F. and a GHSV of about 100 to 800 hr.⁻¹ until theeffluent stream contains less than 1000 ppm. of H₂ O and preferably lessthan 500 ppm. Preferably, a substantially pure and dry hydrogen stream(i.e. less than 20 vol. ppm. H₂ O) is used as the reducing agent in thisreduction step. The reducing agent is contacted with the oxidizedcatalyst at conditions including a temperature of about 400° F. to about1200° F., a GHSV of about 300 to 1000 hr.⁻¹, and a period of time ofabout 0.5 to 10 hours at least effective to bring about the desiredselective reduction of the metallic ingredients. This reductiontreatment may be performed in situ as part of a start-up sequence ifprecautions are taken to predry the plant to a substantially water-freestate and if substantially water-free and hydrocarbon-free hydrogen isused.

Although maintaining the subject catalyst in a substantially sulfur-freestate is an especially preferred mode of operation for the presentinvention, the resulting reduced catalytic composite may in somecircumstances be beneficially subjected to a presulfiding operationdesigned to incorporate in the catalytic composite from about 0.01 toabout 0.5 wt. % sulfur, calculated on an elemental basis. Preferably,this presulfiding treatment takes place in the presence of hydrogen anda suitable sulfur-containing sulfiding reagent such as hydrogen sulfide,lower molecular weight mercaptans, organic sulfides, etc. Typically,this procedure comprises treating the selectively reduced catalyst witha sulfiding reagent such as a mixture of hydrogen and hydrogen sulfidehaving about 10 moles of hydrogen per mole of hydrogen sulfide atconditions sufficient to effect the desired incorporation of sulfur,generally including a temperature ranging from about 50° F up to about1100° F. or more. It is generally a good practice to perform thispresulfiding step under substantially water-free conditions. Althoughnot preferred, it is within the scope of the present invention tomaintain or achieve the sulfided state of the instant catalyst duringuse in the conversion of hydrocarbons by continuously or periodicallyadding a decomposable sulfur-containing compound, such as the onespreviously mentioned, to the reactor containing the catalyst in anamount sufficient to provide about 1 to 500 wt. ppm., preferably 1 to 20wt. ppm. of sulfur based on hydrocarbon charge.

According to the method of the present invention, the dehydrogenatablehydrocarbon is contacted with the multimetallic catalytic compositedescribed above in a dehydrogenation zone maintained at dehydrogenationconditions. This contacting may be accomplished by using the catalyst ina fixed bed system, a moving bed system, a fluidized bed system, or in abatch type operation; however, in view of the danger of attrition lossesof the valuable catalyst and of well-known operational advantages, it ispreferred to use a fixed bed system. In this system, the hydrocarbonfeed stream is preheated by any suitable heating means to the desiredreaction temperature and then passed into a dehydrogenation zonecontaining a fixed bed of the catalyst previously characterized. It is,of course, understood that the dehydrogenation zone may be one or moreseparate reactors with suitable heating means therebetween to insurethat the desired conversion temperature is maintained at the entrance toeach reactor. It is also to be noted that the reactants may be contactedwith the catalyst bed in either upward, downward, or radial flow fashionwith the latter being preferred. In addition, it is to be noted that thereactants may be in the liquid phase, a mixed liquid-vapor phase, or avapor phase when they contact the catalyst, with best results obtainedin the vapor phase.

Although hydrogen is the preferred diluent for use in the subjectdehydrogenation method, in some cases other art-recognized diluents maybe advantageously utilized, either individually or in admixture withhydrogen or with each other, such as steam, methane, ethane, propane,butane, carbon dioxide, and the like diluents. Hydrogen is preferredbecause it serves the dual-function of not only lowering the partialpressure of the dehydrogenatable hydrocarbon, but also of suppressingthe formation of hydrogen-deficient, carbonaceous deposits on thecatalytic composite. Ordinarily, hydrogen is utilized in amountssufficient to insure a hydrogen to hydrocarbon mole ratio of about 1:1to about 20:1, with best results obtained in the range of about 1.5:1 toabout 10:1. The hydrogen stream charged to the dehydrogenation zone willtypically be recycled hydrogen obtained from the effluent stream fromthis zone after a suitable hydrogen separation step. When utilizinghydrogen in the instant process, improved results are obtained if wateror a water-producing substance (such as an alcohol, ketone, ether,aldehyde, or the like oxygen-containing decomposable organic compound)is added to the dehydrogenation zone in an amount calculated on thebasis of equivalent water, corresponding to about 50 to about 10,000 wt.ppm. of the hydrocarbon charge stock, with about 1500 to 5000 wt. ppm.of water giving best results.

Regarding the conditions utilized in the process of the presentinvention, these are generally selected from the dehydrogenationconditions well known to those skilled in the art for the particulardehydrogenatable hydrocarbon which is charged to the process. Morespecifically, suitable conversion temperatures are selected from therange of about 700° to about 1200° F. with a value being selected fromthe lower portion of this range for the more easily dehydrogenatedhydrocarbons such as the long chain normal paraffins and from the higherportion of this range for the more difficulty dehydrogenatedhydrocarbons such as propane, butane, and the like hydrocarbons. Forexample, for the dehydrogenation of C₆ to C₃₀ normal paraffins, bestresults are ordinarily obtained at a temperature of about 800° to about950° F. The pressure utilized is ordinarily selected at a value which isas low as possible consistent with the maintenance of catalyst stabilityand is usually about 0.1 to about 10 atmospheres with best resultsordinarily obtained in the range of about 0.5 to about 3 atmospheres. Inaddition, a liquid hourly space velocity (calculated on the basis of thevolume amount, as a liquid, of hydrocarbon charged to thedehydrogenation zone per hour divided by the volume of the catalyst bedutilized) is selected from the range of about 1 to about 40 hr.⁻¹, withbest results for the dehydrogenation of long chain normal paraffinstypically obtained at a relatively high space velocity of about 25 to 35hr.⁻¹.

Regardless of the details concerning the operation of thedehydrogenation step, an effluent stream will be withdrawn therefrom.This effluent will usually contain unconverted dehydrogenatablehydrocarbons, hydrogen, and products of the dehydrogenation reaction.This stream is typically cooled and passed to a hydrogen-separating zonewherein a hydrogen-rich vapor phase is allowed to separate from ahydrocarbon-rich liquid phase. In general, it is usually desired torecover the unreacted dehydrogenatable hydrocarbon from thishydrocarbon-rich liquid phase in order to make the dehydrogenationprocess economically attractive. This recovery operation can beaccomplished in any suitable manner known to the art such as by passingthe hydrocarbon-rich liquid phase through a bed of suitable adsorbentmaterial which has the capability to selectively retain thedehydrogenated hydrocarbons contained therein or by contacting same witha solvent having a high selectivity for the dehydrogenated hydrocarbon,or by a suitable fractionation scheme where feasible. In the case wherethe dehydrogenated hydrocarbon is a mono-olefin, suitable adsorbentshaving this capability are activated silica gel, activated carbon,activated alumina, various types of specially prepared zeoliticcrystalline alumino-silicates, molecular sieves, and the likeadsorbents. In another typical case, the dehydrogenated hydrocarbons canbe separated from the unconverted dehydrogenatable hydrocarbons byutilizing the inherent capability of the dehydrogenated hydrocarbons toeasily enter into several well-known chemical reactions such asalkylation, oligomerization, halogenation, sulfonation, hydration,oxidation, and the like reactions. Irrespective of how thedehydrogenated hydrocarbons are separated from the unreactedhydrocarbons, a stream containing the unreacted dehydrogenatablehydrocarbons will typically be recovered from this hydrocarbonseparation step and recycled to the dehydrogenation step. Likewise, thehydrogen phase present in the hydrogen-separating zone will be withdrawntherefrom, a portion of it vented from the system in order to remove thenet hydrogen make, and the remaining portion is typically recycledthrough suitable compressing means to the dehydrogenation step in orderto provide diluent hydrogen therefor.

In a preferred embodiment of the present invention wherein long chainnormal paraffin hydrocarbons are dehydrogenated to the correspondingnormal mono-olefins, a preferred mode of operation of this hydrocarbonrecovery step involves an alkylation reaction. In this mode, thehydrocarbon-rich liquid phase withdrawn from the hydrogen-separatingzone is combined with a stream containing an alkylatable aromatic andthe resulting mixture passed to an alkylation zone containing a suitablehighly acid catalyst such as an anhydrous solution of hydrogen fluoride.In the alkylation zone the mono-olefins react with alkylatable aromaticwhile the unconverted normal paraffins remain substantially unchanged.The effluent stream from the alkylation zone can then be easilyseparated, typically by means of a suitable fractionation system, toallow recovery of the unreacted normal paraffins. The resulting streamof unconverted normal paraffins is then usually recycled to thedehydrogenation step of the present invention.

The following working examples are introduced to illustrate further thedehydrogenation method and nonacidic multimetallic catalytic compositeof the present invention. These examples of specific embodiments of thepresent invention are intended to be illustrative rather thanrestrictive.

These examples are all performed in a laboratory scale dehydrogenationplant comprising a reactor, a hydrogen separating zone, heating means,cooling means, pumping means, compressing means, and the likeconventional equipment. In this plant, the feed stream containing thedehydrogenatable hydrocarbon is combined with a hydrogen streamcontaining water in an amount corresponding to about 2000 wt. ppm. ofthe hydrocarbon feed and the resultant mixture heated to the desiredconversion temperature, which refers herein to the temperaturemaintained at the inlet to the reactor. The heated mixture is thenpassed into contact with the instant multimetallic catalyst which ismaintained as a fixed bed of catalyst particles in the reactor. Thepressures reported herein are recorded at the outlet from the reactor.An effluent stream is withdrawn from the reactor, cooled, and passedinto the hydrogen-separating zone wherein a hydrogen gas phase separatesfrom a hydrocarbon-rich liquid phase containing dehydrogenatedhydrocarbons, unconverted dehydrogenatable hydrocarbons, and a minoramount of side products of the dehydrogenation reaction. A portion ofthe hydrogen-rich gas phase is recovered as excess recycle gas with theremaining portion being continuously recycled, after water addition asneeded, through suitable compressing means to the heating zone asdescribed above. The hydrocarbon-rich liquid phase from the separatingzone is withdrawn therefrom and subjected to analysis to determineconversion and selectivity for the desired dehydrogenated hydrocarbon aswill be indicated in the Examples. Conversion numbers of thedehydrogenatable hydrocarbon reported herein are all calculated on thebasis of disappearance of the dehydrogenatable hydrocarbon and areexpressed in mole percent. Similarly, selectivity numbers are reportedon the basis of moles of desired hydrocarbon produced per 100 moles ofdehydrogenatable hydrocarbon converted.

All of the catalysts utilized in these examples are prepared accordingto the following preferred method with suitable modification instoichiometry to achieve the compositions reported in each example.First, an alumina carrier material comprising 1/16 inch spheres havingan apparent bulk density of about 0.3 g/cc is prepared by: forming analumina hydroxyl chloride sol by dissolving substantially pure aluminumpellets in a hydrochloric acid solution, adding hexamethylenetetramineto the resulting alumina sol, gelling the resulting solution by droppingit into an oil bath to form spherical particles of an alumina hydrogel,aging, and washing the resulting particles with an ammoniacal solutionand finally drying, calcining and steaming the aged and washed particlesto form spherical particles of gamma-alumina containing substantiallyless than 0.1 wt. % combined chloride. Additional details as to thismethod of preparing this alumina carrier material are given in theteachings of U.S. Pat. No. 2,620,314.

The resulting gamma-alumina particles are then contacted at suitableimpregnation conditions with an aqueous impregnation solution containingchloroplatinic acid, rhodium nitrate, nickel nitrate, and nitric acid inamounts sufficient to yield a final multimetallic catalytic compositecontaining a uniform dispersion of the hereinafter specified amounts ofplatinum, rhodium and nickel. In the example where the catalyst containsgermanium, it was added by means of an aged solution, comprisinggermanium dissolved in anhydrous alcohol, which solution was admixedwith the impregnation solution. The nitric acid is utilized in thisimpregnation solution in an amount of about 5 wt. % of the aluminaparticles. In order to ensure a uniform dispersion of the metalliccomponents in the carrier material, the impregnation solution ismaintained in contact with the carrier material particles for about 1/2hour at a temperature of about 70° F. with constant agitation. Theimpregnated spheres are then dried at a temperature of about 225° F. forabout an hour and thereafter calcined or oxidized in an air atmospherecontaining about 5 to 25 vol. % H₂ O at a temperature of about 500° F.to about 1000° F. for about 2 to 10 hours effective to convert all ofthe metallic components to the corresponding oxide forms. In general, itis a good practice to thereafter treat the resulting oxidized particleswith an air stream containing about 10 to about 30% steam at atemperature of about 800° F. to about 1000° F. for an additional periodof about 1 to about 5 hours in order to reduce any residual combinedchloride contained in the catalyst to a value of less than 0.5 wt. % andpreferably less than 0.2 wt. %.

In the cases shown in the examples where the catalyst utilized containsan alkali or alkaline earth component, this component is also added tothe oxidized and steam-treated multimetallic catalyst in this secondimpregnation step. This second impregnation step involves contacting theoxidized and steamed multimetallic catalyst with an aqueous solution ofa suitable soluble and decomposable salt of the alkali or alkaline earthcomponent under conditions selected to result in a uniform dispersion ofthis component in the carrier material. For th catalysts utilized in thepresent examples, the salts are lithium nitrate or potassium nitrate.The amounts of the salts of the alkali metal utilized are chosen toresult in a final catalyst having the desired nonacidic characteristics.The resulting alkali or alkaline earth-impregnated particles are thenpreferably dried, oxidized, and steamed in an air atmosphere in much thesame manner as is described above following the first impregnation step.In some cases, it is possible to combine both of these impregnationsteps into a single step, thereby significantly reducing the time andcomplexity of the catalyst manufacturing procedure.

The resulting oxidized catalyst is therefor subjected to a drying stepwhich involves contacting the oxidized particles with a dry air streamat a temperature of about 1050° F., a GHSV of 300 hr.⁻¹ for a period ofabout 10 hours. The dried catalyst is then purged with a dry nitrogenstream and thereafter selectively reduced by contacting with a dryhydrogen stream at conditions including a temperature of about 870° F.,atmospheric pressure and a gas hourly space velocity of about 500 hr.⁻¹,for a period of about 1 to 10 hours effective to reduce substantiallyall of the platinum or palladium, rhodium and nickel components to thecorresponding elemental metal while maintaining the alkali or alkalineearth and/or Group IVA metallic components in a positive oxidationstate.

EXAMPLE I

The reactor is loaded with 100 cc of a catalyst containing, on anelemental basis, 0.375 wt. % platinum, 0.25 wt. % rhodium, 0.25 wt. %nickel, 0.5 wt. % germanium and less than 0.15 wt. % chloride. The feedstream utilized is commercial grade isobutane containing 99.7 wt. %isobutane and 0.3 wt. % normal butane. The feed stream is contacted withthe catalyst at a temperature of 1065° F., a pressure of 10 psig., aliquid hourly space velocity of 4.0 hr.⁻¹, and a hydrogen to hydrocarbonmole ratio of 2:1. The dehydrogenation plant is lined-out at theseconditions and a 20 hour test period commenced. The hydrocarbon productstream from the plant is continuously analyzed by GLC (gas liquidchromatography) and a high conversion of isobutane is observed with ahigh selectivity for isobutylene.

EXAMPLE II

The catalyst contains, on an elemental basis, 0.375 wt. % platinum, 0.5wt. % nickel, 0.1 wt. % rhodium, 0.25 wt. % germanium, 0.6 wt. %lithium, and 0.15 wt. % combined chloride. The feed stream is commercialgrade normal dodecane. The dehydrogenation reactor is operated at atemperature of 870° F., a pressure of 10 psig., a liquid hourly spacevelocity of 32 hr.⁻¹, and a hydrogen to hydrocarbon mole ratio of 8:1.After a line-out period, a 20 hour test period is performed during whichthe average conversion of the normal dodecane is maintained at a highlevel with a selectivity for normal dodecene of about 90%.

EXAMPLE III

The catalyst is the same as utilized in Example II. The feed stream isnormal tetradecane. The conditions utilized are a temperature of 840°F., a pressure of 20 psig., a liquid hourly space velocity of 32 hr.⁻¹,and a hydrogen to hydrocarbon mole ratio of 8:1. After a line-outperiod, a 20 hour test shows an average conversion of about 12%, and aselectivity for normal tetradecene of about 90%.

EXAMPLE IV

The catalyst contains, on an elemental basis, 0.3 wt. % platinum, 0.1wt. % rhodium and 0.2 wt. % nickel, with combined chloride being lessthan 0.2 wt. %. The feed stream is substantially pure cyclohexane. Theconditions utilized are a temperature of 900° F., a pressure of 100psig., a liquid hourly space velocity of 3.0 hr.⁻¹, and a recycle gas tohydrocarbon mole ratio of 4:1. After a line-out period, a 20 hour testis performed with almost quantitative conversion of cyclohexane tobenzene and hydrogen.

EXAMPLE V

The catalyst contains, on an elemental basis, 0.2 wt. % platinum, 0.5wt. % nickel, 0.1 wt. % rhodium, 1.5 wt. % potassium, and less than 0.2wt. % combined chloride. The feed stream is commercial gradeethyl-benzene. The conditions utilized are a pressure of 15 psig., aliquid hourly space velocity of 32 hr.⁻¹, a temperature of 1050° F., anda hydrogen to hydrocarbon mole ratio of 8:1. During a 20 hour testperiod, 85% or more of equilibrium conversion of the ethylbenzene isobserved. The selectivity for styrene is about 95%.

It is intended to cover by the following claims, all changes andmodifications of the above disclosure of the present invention whichwould be self-evident to a man of ordinary skill in thecatalyst-formulation art or in the hydrocarbon dehydrogenation art.

I claim as my invention:
 1. A method for dehydrogenating adehydrogenatable hydrocarbon comprising contacting the hydrocarbon, atdehydrogenation conditions, with a catalytic composite comprising aporous carrier material containing, on an elemental basis, about 0.01 toabout 2 wt. % platinum or palladium, about 0.01 to about 2 wt. %rhodium, and about 0.01 to about 5 wt. % nickel; wherein the platinum orpalladium, rhodium and nickel are uniformly dispersed throughout theporous carrier material; and wherein substantially all of the platinumor palladium, rhodium and nickel are present in the elemental metallicstate.
 2. A method as defined in claim 1 wherein the dehydrogenatablehydrocarbon is admixed with hydrogen when it contacts the catalyticcomposite.
 3. A method as defined in claim 1 wherein the porous carriermaterial is a refractory inorganic oxide.
 4. A method as defined inclaim 3 wherein the refractory inorganic oxide is alumina.
 5. A methodas defined in claim 1 wherein the dehydrogenatable hydrocarbon is anormal paraffin hydrocarbon containing 4 to 30 carbon atoms permolecule.
 6. A method as defined in claim 1 wherein the dehydrogenatablehydrocarbon is a naphthene.
 7. A method as defined in claim 1 whereinthe dehydrogenatable hydrocarbon is an alkylaromatic, the alkyl group ofwhich contains about 2 to 6 carbon atoms.
 8. A method as defined inclaim 2 wherein the dehydrogenation conditions include a temperature of700° to about 1200° F., a pressure of 0.1 to 10 atmospheres, a LHSV of 1to 40 hr.⁻¹, and a hydrogen to hydrocarbon mole ratio of about 1:1 toabout 20:1.
 9. A method as defined in claim 1 wherein the compositecontains, on an elemental basis, about 0.05 to about 1 wt. % platinum orpalladium, about 0.05 to about 1 wt. % rhodium and about 0.05 to about 2wt. % nickel.
 10. A method as defined in claim 1 wherein the metalscontent of the catalytic composite is adjusted so that the atomic ratioof rhodium to platinum or palladium is about 0.1:1 to about 2:1 and theatomic ratio of nickel to platinum or palladium is about 0.2:1 to about40:1.
 11. A method as defined in claim 1 wherein the catalytic compositecontains, on an elemental basis, about 0.01 to about 5 wt. % Group IVAmetal and wherein substantially all of the Group IVA metal is present inan oxidation state above that of the corresponding elemental metal. 12.A method as defined in claim 11 wherein the Group IVA metal isgermanium.
 13. A method as defined in claim 11 wherein the Group IVAmetal is tin.
 14. A method as defined in claim 11 wherein the Group IVAmetal is lead.
 15. A method for dehydrogenating a dehydrogenatablehydrocarbon comprising contacting the hydrocarbon, at dehydrogenationconditions, with a nonacidic catalytic composite comprising a porouscarrier material containing, on an elemental basis, about 0.01 to about2 wt. % platinum or palladium, about 0.01 to about 2 wt. % rhodium,about 0.1 to about 5 wt. % alkali metal or alkaline earth metal, andabout 0.01 to about 5 wt. % nickel; wherein the platinum or palladium,rhodium, nickel and alkali metal or alkaline earth metal are uniformlydispersed throughout the porous carrier material; wherein substantiallyall of the platinum or palladium, rhodium and nickel are present in theelemental metallic state; and wherein substantially all of the alkalimetal or alkaline earth metal is present in an oxidation state abovethat of the elemental metal.
 16. A method as defined in claim 15 whereinthe porous carrier material is a refractory inorganic oxide.
 17. Amethod as defined in claim 16 wherein the refractory inorganic oxide isalumina.
 18. A method as defined in claim 15 wherein the alkali metal oralkaline earth metal is potassium.
 19. A method as defined in claim 15wherein the alkali metal or alkaline earth metal is lithium.
 20. Amethod as defined in claim 15 wherein the composite contains, on anelemental basis, about 0.05 to about 1 wt. % platinum or palladium,about 0.01 to about 2 wt. % rhodium, about 0.05 to about 2 wt. % nickeland about 0.25 to about 3.5 wt. % alkali metal or alkaline earth metal.21. A method as defined in claim 15 wherein the metals contents thereofis adjusted so that the atomic ratio of rhodium to platinum or palladiumis about 0.1:1 to about 2:1, the atomic ratio of alkali metal oralkaline earth metal to platinum or palladium is about 5:1 to about100:1 and the atomic ratio of nickel to platinum or palladium is about0.2:1 to 40:1.
 22. A method as defined in claim 15 wherein the catalyticcomposite contains, on an elemental basis, about 0.01 to about 5 wt. %Group IVA metal and wherein substantially all of the Group IVA metal ispresent in an oxidation state above that of the corresponding elementalmetal.
 23. A method as defined in claim 22 wherein the Group IVA metalis germanium.
 24. A method as defined in claim 22 wherein the Group IVAmetal is tin.
 25. A method as defined in claim 22 wherein the Group IVAmetal is lead.
 26. A method as defined in claim 15 wherein thedehydrogenatable hydrocarbon is admixed with hydrogen when it contactsthe catalytic composite.
 27. A method as defined in claim 15 wherein thedehydrogenatable hydrocarbon is a normal paraffin hydrocarbon containingabout 4 to 30 carbon atoms per molecule.
 28. A method as defined inclaim 15 wherein the dehydrogenatable hydrocarbon is a normal paraffinhydrocarbon containing about 10 to about 18 carbon atoms per molecule.29. A method as defined in claim 15 wherein the dehydrogenatablehydrocarbon is an alkylaromatic, the alkyl group of which contains about2 to 6 carbon atoms.
 30. A method as defined in claim 15 wherein thedehydrogenatable hydrocarbon is a naphthene.
 31. A method as defined inclaim 26 wherein the dehydrogenation conditions include a temperature ofabout 700° to about 1200° F., a pressure of about 0.1 to about 10atmospheres, an LHSV of about 1 to 40 hr.⁻¹, and a hydrogen tohydrocarbon mole ratio of about 1:1 to about 20:1.
 32. A method asdefined in claim 26 wherein the contacting is performed in the presenceof water or a water-producing substance in an amount corresponding toabout 50 to about 10,000 wt. ppm. based on hydrocarbon charge.